From the lab: Better biomaterials for medical implants

We do not yet have a material that is easily accepted inside the human body. A variety of materials are used for the different kinds of functions they are intended to perform once inserted inside. At our group, we have been trying to develop a comprehensive understanding of how biological cells in human bodies interact with a material surface. The idea is to recreate conditions that allow human cells to grow and function normally on a synthetic material. If we are able to do that, these materials, or biomaterials as we like to call them, can be used as various implants.

We have been using stem cells, isolated from the bone marrow, for our studies. Stem cells, unlike many other cells in human body, are unspecialised cells. For example, muscle cells have very specific functionality: they are able to expand or contract, in a certain way, when mechanical stress is applied. Similarly, cardiac cells, bone cells and neural cells also have specific functionality. In contrast, stem cells do not have any specific functionality but can develop into one of these specific cells under specific physiological environment.

We have been trying to grow these stem cells on new materials and provide external stimulus, like electric field or magnetic field to observe what functionality these stem cells adopt. We then try to see whether we can control this process, whether we can guide the stem cells to adopt a particular behaviour and develop into a cardiac cell or neural cell or bone cell. We have been carrying out these investigations for some years now and have shown that the stem cells can indeed be guided to perform a specific function by intelligent choice of materials and external stimulus.

More recently, we have been trying to develop materials that will imitate our bones. A substantial proportion of natural bone comprises the mineral hydroxylapatite (HA), which is a type of Calcium phosphate. We therefore tried to create synthetic materials composed of hydroxylapatite to test whether they can be given the properties of natural bone. To name a few, we have prepared two composites of hydroxylapatite, one with Titanium and the other with Barium Titanate (BaTiO3). The HA-Ti composite has shown very good resistance against fracture and has already attracted a lot of attention in scientific circles. The other composite, with BaTiO3, shows piezoelectric properties, that is, it generates electricity when mechanical stress is applied to it. The piezoelectric property, available in natural bone, is extremely difficult to obtain in synthetic materials. Both these composites, and their potential to be developed into a bone-imitating material, have been noticed for the first time.

This search for a suitable biomaterial is aimed at improving the healing time in patients receiving the implants. Currently, it takes a long time for a patient undergoing an orthopaedic surgery to get healed. This is because the materials currently used take long to get integrated with the muscles and bone tissues. More suitable materials can reduce this healing time. In addition, these also reduce the risk of rejection by the body, because of which we increasingly see patients having to undergo revision surgeries.